Determining the exact location of a receiver (e.g. a mobile phone) in an environment can be quite challenging, especially when the receiver is located in an urban environment, or is located within a building. Imprecise estimates of the receiver's position may have “life or death” consequences for the user. For example, an imprecise position estimate of a receiver, such as a mobile phone operated by a user calling 911, can delay emergency personnel response times. In less dire situations, imprecise estimates of the receiver's position can negatively impact navigation applications by sending a user to the wrong location, or taking too long to provide accurate directions.
Positioning systems used to estimate the position of the receiver, like the Global Positioning System (GPS), have been in use for many years. Unfortunately, poor signal conditions found in urban or indoor environments may degrade the performance of these conventional positioning systems. To improve positioning accuracy in urban and indoor environments, GPS may be augmented by positioning systems that use terrestrial transmitters, however it is still the case that when the receiver is within an urban area or inside a building, the augmented positioning system is often ineffective. Thus, new approaches that solve the above problems are needed.
Like reference numbers and designations in the drawings indicate like elements.